1. Field of the Invention
Methods consistent with the present invention relate to location tracking in a coordinator-based wireless network.
2. Description of the Related Art
A recent trend in networking is to interconnect devices that need to exchange data, in addition to computers. In the past, wired networking was the norm. But, the disadvantages of the wired networking, such as wiring construction and limited mobility, necessitate wireless communication technology. Wireless Local Area Network (WLAN) and Wireless Personal Area Network (WPAN) standards are being developed. A WPAN has a range of 10 m, while WLAN has a range of 50 m to 100 m. The WPAN is more suitable for electronic home appliances in terms of mobility and range because it consumes less power and supports Ad-hoc networking.
The coordinator-based wireless network uses a coordinator to manage the communication time and competition mode of the wireless network. It uses many of the protocols decided by IEEE 802.15 working group, which was founded to establish a WPAN standard. The IEEE 802.15 working group is divided into four task groups. TG 1 works on the standards for WPAN based on Bluetooth 1.x. TG 2 studies co-existence of the wireless networks. TG 3 studies Ultra Wideband (UWB), which provides a high transmission rate of 20 Mbps or more with low power consumption. TG 4 studies Low Rate WPAN (LR-WPAN), a technology to provide a low transmission rate (maximum 250 kbps) at a low power consumption.
LR WPAN is concerned with low-cost communication networks that require low data transmission rates. The IEEE 802.15.4 standard known as “ZigBee” is a wireless transmission technology for networks of low cost, low power devices such as wireless integration remote controllers, home appliance controllers, building management controllers and toys. The ZigBee group was established in July, 2000 and since then it has finished working on the standards for the physical layer and MAC.
The standard specifies that the transmission is 250 kbps (16 channels in the 2.4 GHz band) or 40 kbps/20 kbps (10 channels in the 915 MHz band or one channel in the 868 MHz band), and the range is 1 m to 100 m.
Work is still being done on the upper layer, which includes a network layer. Fifty companies including Philips, Motorola, Honeywell, Mitsubishi, Invensys, and Samsung are promoters in a ZigBee Alliance in order to supplement the existing standard by adding ad-hoc wireless networking and a network protocol for dispersed devices.
ZigBee does the job of preparing check lists and specifically defining applications to practically perform the interoperability test. The requirements of IEEE 802.15.4 include low power consumption, low cost, and simple infrastructure. These requirements are necessary to network sensors and control devices.
IEEE 802.15.4a defines the standard for a low-rate location-based network using Ultra Wideband (UWB), which is a new networking technology implementing a precise location awareness service making a ubiquitous environment achievable.
IEEE 802.15.4a is a subgroup of 802.15.4 and it uses the same Medium Access Control (MAC) as 802.15.4, but substitutes UWB for the Physical Layer (PHY). But, it does not define a location tracking protocol. So, a location-based service has to be added to the coordinate-based wireless network to embody the location tracking technology of IEEE 802.15.4a. A privacy protection service should also be added in a manner that allows a user control over the location tracking.